Method and apparatus for load distribution using heterogeneous radio access technologies in communication system supporting vehicle-to-everything communication

ABSTRACT

An operation method of a first communication node located in a vehicle may include: performing V2X communication with a second communication node using an original resource according to an original SPS configuration; when a congestion level in the original resource is not less than a predetermined threshold and at least one target base station supporting V2X communication is discovered, generating new SPS configuration to be applied to the serving base station and the at least one target base station by changing original SPS configuration; performing a message transmission and reception procedure with the at least one target base station for delivery of new SPS configuration; and performing V2X communication with the second communication node using first resource scheduled by the serving base station based on new SPS configuration and second resource scheduled by the at least one target base station based on new SPS configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation to U.S. patent application Ser. No.16/052,597, filed on Jul. 11, 2018 claims the benefit of priority toU.S. Provisional Patent Application 62/628,600, filed on Feb. 9, 2018 inthe U.S. Patent and Trademark Office, and Korean Patent Application No.10-2018-0056085, filed on May 16, 2018 in the Korean IntellectualProperty Office (KIPO), the entire contents of which are incorporatedherein by reference.

BACKGROUND 1. Technical Field

The present disclosure relates generally to vehicle-to-everything (V2X)communication, and more specifically, to a method and an apparatus forload distribution using heterogeneous radio access technologies (RATs).

2. Related Art

A fifth-generation (5G) communication system (e.g., New Radio (NR)communication system) which uses a frequency band higher than afrequency band of a fourth-generation (4G) communication system (e.g.,Long Term Evolution (LTE) communication system or LTE-Advanced (LTE-A)communication system) as well as the frequency band of the 4Gcommunication system has been considered for processing of wirelessdata. The 5G communication system can support Enhanced Mobile Broadband(eMBB) communications, Ultra-Reliable and Low-Latency communications(URLLC), massive Machine Type Communications (mMTC), and the like.

The 4G communication system and 5G communication system can supportVehicle-to-Everything (V2X) communications. The V2X communicationssupported in a cellular communication system such as the 4Gcommunication system, the 5G communication system, and the like may bereferred to as “Cellular-V2X (C-V2X) communications.” The V2Xcommunications (e.g., C-V2X communications) may includeVehicle-to-Vehicle (V2V) communications, Vehicle-to-Infrastructure (V2I)communications, Vehicle-to-Pedestrian (V2P) communication,Vehicle-to-Network (V2N) communication, and the like.

In the cellular communication systems, the V2X communications (e.g.,C-V2X communications) may be performed based on “sidelink” communicationtechnologies (e.g., Proximity based Services (ProSe) communicationtechnology, Device-to-Device (D2D) communication technology, or thelike). For example, sidelink channels for vehicles participating in V2Vcommunications can be established, and communications between thevehicles can be performed using the sidelink channels.

In a cellular communication system supporting V2X communications (e.g.,C-V2X communications), a vehicle, in which a communication node isdisposed, may use a carrier configured based on a semi-persistentscheduling (SPS) scheme to communicate with a communication node (e.g.,a communication node located in another vehicle, a communication nodelocated in the infrastructure, or a communication node carried by aperson). However, in a case that a load of the carrier configured basedon the SPS scheme increases, data of the vehicle, often having highreliability and low latency requirements, such as DecentralizedEnvironment Notification Message (DENM), Cooperative Awareness Message(CAM), and the like, may not be successfully transmitted or received. Inthis case, serious problems may occur due to a communication failure ofthe vehicle.

SUMMARY

Accordingly, embodiments of the present disclosure provide a method andan apparatus for load distribution using heterogeneous RATs when aSemi-Persistent Scheduling (SPS) scheme is used in a communicationsystem supporting V2X communications.

According to embodiments of the present disclosure, an operation methodof a first communication node located in a vehicle, in a communicationsystem supporting Vehicle-to-Everything (V2X) communication can include:performing V2X communication with a second communication node using anoriginal resource according to an original Semi-Persistent Scheduling(SPS) configuration set by a serving base station; when a congestionlevel in the original resource is greater than or equal to apredetermined threshold and at least one target base station supportingthe V2X communication is discovered, generating a new SPS configurationto be applied to the serving base station and the at least one targetbase station by changing the original SPS configuration; performing amessage transmission and reception procedure with the at least onetarget base station for delivery of the new SPS configuration; andperforming the V2X communication with the second communication nodeusing a first resource scheduled by the serving base station based onthe new SPS configuration and a second resource scheduled by the atleast one target base station based on the new SPS configuration.

The performing of the message transmission and reception procedure maycomprise transmitting, to the at least one target base station, a radioresource control (RRC) connection request message requesting aconnection for applying the new SPS configuration; receiving an RRCconnection setup message from the at least one target base station, theRRC connection setup message being a response to the RRC connectionrequest message; transmitting an RRC connection setup complete messageincluding an identifier of the serving base station and the new SPSconfiguration to the at least one target base station when a connectionestablishment between the first communication node and the at least onetarget base station is completed; and receiving, from the at least onetarget base station, an RRC connection reconfiguration messageindicating an application of the new SPS configuration.

The performing of the message transmission and reception procedure maycomprise transmitting, to the at least one target base station, userequipment (UE) assistance information including an indicator requestingan application of the new SPS configuration, an identifier of theserving base station, and the new SPS configuration; and receiving, fromthe at least one target base station, an RRC connection reconfigurationmessage indicating the application of the new SPS configuration.

The operation method may further comprise transmitting, to the servingbase station, UE assistance information including at least oneidentifier of the at least one target base station and the new SPSconfiguration.

The V2X communication using the first resource and the second resourcebased on the new SPS configuration may be performed when a messagerequesting application of the new SPS configuration is received from theserving base station and the at least one target base station.

A radio access technology (RAT) supported by the serving base stationmay be different from a RAT supported by the at least one target basestation.

When a sum of a number of serving base stations and a number of the atleast one target base station is N and a transmission interval of theoriginal SPS configuration is T transmission time intervals (TTIs), atransmission interval of the new SPS configuration may be set to N×TTTIs, N being an integer greater than or equal to 2, and T being aninteger greater than or equal to 1.

An offset between transmission intervals of the N base stations may beset to T TTIs in the new SPS configuration.

When a sum of a number of serving base stations and a number of the atleast one target base station is N and a transmission interval of theoriginal SPS configuration is T TTIs, a transmission interval of the newSPS configuration may be set to T TTIs, a size of data to be transmittedthrough each of the N base stations in the new SPS configuration mayequal (a size of total data to be transmitted to the secondcommunication node)/N, N being an integer greater than or equal to 2,and T being an integer greater than or equal to 1.

When a sum of a number of serving base stations and a number of the atleast one target base station is N and a transmission interval of theoriginal SPS configuration is T TTIs, a transmission interval of the newSPS configuration may be set to T TTIs, a size of data to be transmittedthrough each of the N base stations in the new SPS configuration may beinversely proportional to a channel congestion of each of the N basestations, N being an integer greater than or equal to 2, and T being aninteger greater than or equal to 1.

Furthermore, in accordance with embodiments of the present disclosure,an operation method of a first communication node located in a vehicle,in a communication system supporting Vehicle-to-Everything (V2X)communication can include: performing V2X communication with a secondcommunication node using an original resource according to an originalSemi-Persistent Scheduling (SPS) configuration set by a serving basestation; when a congestion level in the original resource is greaterthan or equal to a predetermined threshold and at least one target basestation supporting the V2X communication is discovered, transmittinguser equipment (UE) assistance information including at least oneidentifier of the at least one target base station to the serving basestation; receiving, from the serving base station, a message including anew SPS configuration to be applied to the serving base station and theat least one target base station; performing a message transmission andreception procedure with the at least one target base station fordelivery of the new SPS configuration; and performing the V2Xcommunication with the second communication node using a first resourcescheduled by the serving base station based on the new SPS configurationand a second resource scheduled by the at least one target base stationbased on the new SPS configuration.

The UE assistance information may further include an indicatorrequesting load distribution using the at least one target base station.

The message including a new SPS configuration may be a radio resourcecontrol (RRC) connection reconfiguration message.

The performing of the message transmission and reception procedure mayinclude transmitting, to the at least one target base station, an RRCconnection request message requesting a connection for applying the newSPS configuration; receiving an RRC connection setup message from the atleast one target base station, the RRC connection setup message being aresponse to the RRC connection request message; transmitting an RRCconnection setup complete message including an identifier of the servingbase station and the new SPS configuration to the at least one targetbase station when a connection establishment between the firstcommunication node and the at least one target base station iscompleted; and receiving, from the at least one target base station, anRRC connection reconfiguration message indicating an application of thenew SPS configuration.

The performing of the message transmission and reception procedure may finclude transmitting, to the at least one target base station, UEassistance information including an indicator requesting application ofthe new SPS configuration, an identifier of the serving base station,and the new SPS configuration; and receiving, from the at least onetarget base station, an RRC connection reconfiguration messageindicating an application of the new SPS configuration.

A radio access technology (RAT) supported by the serving base stationmay be different from a RAT supported by the at least one target basestation.

When a sum of a number of serving base stations and a number of the atleast one target base station is N and a transmission interval of theoriginal SPS configuration is T transmission time intervals (TTIs), atransmission interval of the new SPS configuration may be set to N×TTTIs, N being an integer greater than or equal to 2, and T being aninteger greater than or equal to 1.

An offset between transmission intervals of the N base stations may beset to T TTIs in the new SPS configuration.

When a sum of a number of serving base stations and a number of the atleast one target base station is N and a transmission interval of theoriginal SPS configuration is T TTIs, a transmission interval of the newSPS configuration may be set to T TTIs, a size of data to be transmittedthrough each of the N base stations in the new SPS configuration mayequal (a size of total data to be transmitted to the secondcommunication node)/N, N being an integer greater than or equal to 2,and T being an integer greater than or equal to 1.

When a sum of a number of serving base stations and a number of the atleast one target base station is N and a transmission interval of theoriginal SPS configuration is T TTIs, a transmission interval of the newSPS configuration may be set to T TTIs, a size of data to be transmittedthrough each of the N base stations in the new SPS configuration may beinversely proportional to a channel congestion of each of the N basestations, N being an integer greater than or equal to 2, and T being aninteger greater than or equal to 1.

According to the embodiments of the present disclosure, when a SPSscheme is used in a communication system supporting V2X communications,a SPS configuration can be changed based on CBRs measured by a vehicle,and V2X communication can be performed through resources allocated by aplurality of base stations (e.g., a plurality of base stationssupporting different RATs) to which the changed SPS configuration isapplied. That is, when a load on a resource configured by a base stationsupporting a first RAT (e.g., 4G communication technology) suddenlyincrease, the load can be distributed through a base station supportinga second RAT (e.g., 5G communication technology). Accordingly, messageshaving high reliability and low latency requirements such asDecentralized Environment Notification Message (DENM), CooperativeAwareness Message (CAM), messages for platooning services, messages foradvanced driving services, messages for extended sensor services,messages for remote driving services, and the like can be successfullytransmitted and received. Therefore, quality of service (QoS) for theV2X communications can be enhanced, and the performance of thecommunication system can be improved.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure will become more apparent bydescribing in detail embodiments of the present disclosure withreference to the accompanying drawings, in which:

FIG. 1 is a conceptual diagram illustrating V2X communication scenarios;

FIG. 2 is a conceptual diagram illustrating embodiments of a cellularcommunication system;

FIG. 3 is a conceptual diagram illustrating embodiments of acommunication node constituting a cellular communication system;

FIG. 4 is a block diagram illustrating embodiments of a user planeprotocol stack of an UE performing sidelink communication;

FIG. 5 is a block diagram illustrating a first embodiment of a controlplane protocol stack of an UE performing sidelink communication;

FIG. 6 is a block diagram illustrating a second embodiment of a controlplane protocol stack of an UE performing sidelink communication;

FIG. 7 is a sequence chart illustrating a first embodiment of a loaddistribution method using heterogeneous RATs;

FIG. 8 is a sequence chart illustrating a second embodiment of a loaddistribution method using heterogeneous RATs;

FIG. 9 is a sequence chart illustrating a third embodiment of a loaddistribution method using heterogeneous RATs; and

FIG. 10 is a sequence chart illustrating a fourth embodiment of a loaddistribution method using heterogeneous RATs.

It should be understood that the above-referenced drawings are notnecessarily to scale, presenting a somewhat simplified representation ofvarious preferred features illustrative of the basic principles of thedisclosure. The specific design features of the present disclosure,including, for example, specific dimensions, orientations, locations,and shapes, will be determined in part by the particular intendedapplication and use environment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing embodiments of the presentdisclosure. Thus embodiments of the present disclosure may be embodiedin many alternate forms and should not be construed as limited toembodiments of the present disclosure set forth herein.

Accordingly, while the present disclosure is capable of variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and will herein be described indetail. It should be understood, however, that there is no intent tolimit the present disclosure to the particular forms disclosed, but onthe contrary, the present disclosure is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of thepresent disclosure. Like numbers refer to like elements throughout thedescription of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(i.e., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this present disclosure belongs.It will be further understood that terms, such as those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g., fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

Additionally, it is understood that one or more of the below methods, oraspects thereof, may be executed by at least one control unit. The term“control unit” may refer to a hardware device that includes a memory anda processor. The memory is configured to store program instructions, andthe processor is specifically programmed to execute the programinstructions to perform one or more processes which are describedfurther below. The control unit may control operation of units, modules,parts, or the like, as described herein. Moreover, it is understood thatthe below methods may be executed by an apparatus (e.g., communicationnode) comprising the control unit in conjunction with one or more othercomponents, as would be appreciated by a person of ordinary skill in theart.

Furthermore, the control unit of the present disclosure may be embodiedas non-transitory computer readable media containing executable programinstructions executed by a processor, controller or the like. Examplesof the computer readable mediums include, but are not limited to, ROM,RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives,smart cards and optical data storage devices. The computer readablerecording medium can also be distributed throughout a computer networkso that the program instructions are stored and executed in adistributed fashion, e.g., by a telematics server or a Controller AreaNetwork (CAN).

Hereinafter, embodiments of the present disclosure will be described ingreater detail with reference to the accompanying drawings. In order tofacilitate general understanding in describing the present disclosure,the same components in the drawings are denoted with the same referencesigns, and repeated description thereof will be omitted.

FIG. 1 is a conceptual diagram illustrating V2X communication scenarios.

As shown in FIG. 1, the V2X communications may includeVehicle-to-Vehicle (V2V) communications, Vehicle-to-Infrastructure (V2I)communications, Vehicle-to-Pedestrian (V2P) communications,Vehicle-to-Network (V2N) communications, and the like. The V2Xcommunications may be supported by a cellular communication system(e.g., a cellular communication system 140), and the V2X communicationssupported by the cellular communication system 140 may be referred to as“Cellular-V2X (C-V2X) communications.” Here, the cellular communicationsystem 140 may include the 4G communication system (e.g., LTEcommunication system or LTE-A communication system), the 5Gcommunication system (e.g., NR communication system), and the like.

The V2V communications may include communications between a firstvehicle 100 (e.g., a communication node located in the vehicle 100) anda second vehicle 110 (e.g., a communication node located in the vehicle110). Various driving information such as velocity, heading, time,position, and the like may be exchanged between the vehicles 100 and 110through the V2V communications. For example, autonomous driving (e.g.,platooning) may be supported based on the driving information exchangedthrough the V2V communications. The V2V communications supported in thecellular communication system 140 may be performed based on sidelinkcommunication technologies (e.g., ProSe and D2D communicationtechnologies, and the like). In this case, the communications betweenthe vehicles 100 and 110 may be performed using at least one sidelinkchannel established between the vehicles 100 and 110.

The V2I communications may include communications between the firstvehicle 100 (e.g., the communication node located in the vehicle 100)and an infrastructure (e.g., road side unit (RSU)) 120 located on aroadside. The infrastructure 120 may also be a traffic light or a streetlight which is located on the roadside. For example, when the V2Icommunications are performed, the communications may be performedbetween the communication node located in the first vehicle 100 and acommunication node located in a traffic light. Traffic information,driving information, and the like may be exchanged between the firstvehicle 100 and the infrastructure 120 through the V2I communications.The V2I communications supported in the cellular communication system140 may also be performed based on sidelink communication technologies(e.g., ProSe and D2D communication technologies, and the like). In thiscase, the communications between the vehicle 100 and the infrastructure120 may be performed using at least one sidelink channel establishedbetween the vehicle 100 and the infrastructure 120.

The V2P communications may include communications between the firstvehicle 100 (e.g., the communication node located in the vehicle 100)and a person 130 (e.g., a communication node carried by the person 130).The driving information of the first vehicle 100 and movementinformation of the person 130 such as velocity, heading, time, position,and the like may be exchanged between the vehicle 100 and the person 130through the V2P communications. The communication node located in thevehicle 100 or the communication node carried by the person 130 maygenerate an alarm indicating a danger by judging a dangerous situationbased on the obtained driving information and movement information. TheV2P communications supported in the cellular communication system 140may be performed based on sidelink communication technologies (e.g.,ProSe and D2D communication technologies, and the like). In this case,the communications between the communication node located in the vehicle100 and the communication node carried by the person 130 may beperformed using at least one sidelink channel established between thecommunication nodes.

The V2N communications may include communications between the firstvehicle 100 (e.g., the communication node located in the vehicle 100)and a server connected through the cellular communication system 140.The V2N communications may be performed based on the 4G communicationtechnology (e.g., LTE or LTE-A) or the 5G communication technology(e.g., NR). Also, the V2N communications may be performed based on aWireless Access in Vehicular Environments (WAVE) communicationtechnology or a Wireless Local Area Network (WLAN) communicationtechnology which is defined in Institute of Electrical and ElectronicsEngineers (IEEE) 802.11, or a Wireless Personal Area Network (WPAN)communication technology defined in IEEE 802.15.

Meanwhile, the cellular communication system 140 supporting the V2Xcommunications may be configured as follows.

FIG. 2 is a conceptual diagram illustrating embodiments of a cellularcommunication system.

As shown in FIG. 2, a cellular communication system may include anaccess network, a core network, and the like. The access network mayinclude a base station 210, a relay 220, User Equipments (UEs) 231through 236, and the like. The UEs 231 through 236 may includecommunication nodes located in the vehicles 100 and 110 of FIG. 1, thecommunication node located in the infrastructure 120 of FIG. 1, thecommunication node carried by the person 130 of FIG. 1, and the like.When the cellular communication system supports the 4G communicationtechnology, the core network may include a serving gateway (S-GW) 250, apacket data network (PDN) gateway (P-GW) 260, a mobility managemententity (MME) 270, and the like.

When the cellular communication system supports the 5G communicationtechnology, the core network may include a user plane function (UPF)250, a session management function (SMF) 260, an access and mobilitymanagement function (AMF) 270, and the like. Alternatively, when thecellular communication system operates in a Non-Stand Alone (NSA) mode,the core network constituted by the S-GW 250, the P-GW 260, and the MME270 may support the 5G communication technology as well as the 4Gcommunication technology, or the core network constituted by the UPF250, the SMF 260, and the AMF 270 may support the 4G communicationtechnology as well as the 5G communication technology.

Also, when the cellular communication system supports a network slicingtechnique, the core network may be divided into a plurality of logicalnetwork slices. For example, a network slice supporting V2Xcommunications (e.g., a V2V network slice, a V2I network slice, a V2Pnetwork slice, a V2N network slice, etc.) may be configured, and the V2Xcommunications may be supported through the V2X network slice configuredin the core network.

The communication nodes (e.g., base station, relay, UE, S-GW, P-GW, MME,UPF, SMF, AMF, etc.) comprising the cellular communication system mayperform communications by using at least one communication technologyamong a code division multiple access (CDMA) technology, a time divisionmultiple access (TDMA) technology, a frequency division multiple access(FDMA) technology, an orthogonal frequency division multiplexing (OFDM)technology, a filtered OFDM technology, an orthogonal frequency divisionmultiple access (OFDMA) technology, a single carrier FDMA (SC-FDMA)technology, a non-orthogonal multiple access (NOMA) technology, ageneralized frequency division multiplexing (GFDM) technology, a filterbank multi-carrier (FBMC) technology, a universal filtered multi-carrier(UFMC) technology, and a space division multiple access (SDMA)technology.

The communication nodes (e.g., base station, relay, UE, S-GW, P-GW, MME,UPF, SMF, AMF, etc.) comprising the cellular communication system may beconfigured as follows.

FIG. 3 is a conceptual diagram illustrating embodiments of acommunication node constituting a cellular communication system.

As shown in FIG. 3, a communication node 300 may comprise at least oneprocessor 310, a memory 320, and a transceiver 330 connected to anetwork for performing communications. Also, the communication node 300may further comprise an input interface device 340, an output interfacedevice 350, a storage device 360, and the like. Each component includedin the communication node 300 may communicate with each other asconnected through a bus 370.

However, each of the components included in the communication node 300may be connected to the processor 310 via a separate interface or aseparate bus rather than the common bus 370. For example, the processor310 may be connected to at least one of the memory 320, the transceiver330, the input interface device 340, the output interface device 350,and the storage device 360 via a dedicated interface.

The processor 310 may execute at least one instruction stored in atleast one of the memory 320 and the storage device 360. The processor310 may refer to a central processing unit (CPU), a graphics processingunit (GPU), or a dedicated processor on which methods in accordance withembodiments of the present disclosure are performed. Each of the memory320 and the storage device 360 may include at least one of a volatilestorage medium and a non-volatile storage medium. For example, thememory 320 may comprise at least one of read-only memory (ROM) andrandom access memory (RAM).

Referring again to FIG. 2, in the communication system, the base station210 may form a macro cell or a small cell, and may be connected to thecore network via an ideal backhaul or a non-ideal backhaul. The basestation 210 may transmit signals received from the core network to theUEs 231 through 236 and the relay 220, and may transmit signals receivedfrom the UEs 231 through 236 and the relay 220 to the core network. TheUEs 231, 232, 234, 235 and 236 may belong to cell coverage of the basestation 210. The UEs 231, 232, 234, 235 and 236 may be connected to thebase station 210 by performing a connection establishment procedure withthe base station 210. The UEs 231, 232, 234, 235 and 236 may communicatewith the base station 210 after being connected to the base station 210.

The relay 220 may be connected to the base station 210 and may relaycommunications between the base station 210 and the UEs 233 and 234.That is, the relay 220 may transmit signals received from the basestation 210 to the UEs 233 and 234, and may transmit signals receivedfrom the UEs 233 and 234 to the base station 210. The UE 234 may belongto both of the cell coverage of the base station 210 and the cellcoverage of the relay 220, and the UE 233 may belong to the cellcoverage of the relay 220. That is, the UE 233 may be located outsidethe cell coverage of the base station 210. The UEs 233 and 234 may beconnected to the relay 220 by performing a connection establishmentprocedure with the relay 220. The UEs 233 and 234 may communicate withthe relay 220 after being connected to the relay 220.

The base station 210 and the relay 220 may support multiple-inputmultiple-output (MIMO) technologies (e.g., single user (SU)-MIMO, multiuser (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP)communication technologies, carrier aggregation (CA) communicationtechnologies, unlicensed band communication technologies (e.g., LicensedAssisted Access (LAA), enhanced LAA (eLAA), etc.), sidelinkcommunication technologies (e.g., ProSe communication technology, D2Dcommunication technology), or the like. The UEs 231, 232, 235 and 236may perform operations corresponding to the base station 210 andoperations supported by the base station 210. The UEs 233 and 234 mayperform operations corresponding to the relays 220 and operationssupported by the relays 220.

Here, the base station 210 may be referred to as a Node B (NB), anevolved Node B (eNB), a base transceiver station (BTS), a radio remotehead (RRH), a transmission reception point (TRP), a radio unit (RU), aroadside unit (RSU), a radio transceiver, an access point, an accessnode, or the like. The relay 220 may be referred to as a small basestation, a relay node, or the like. Each of the UEs 231 through 236 maybe referred to as a terminal, an access terminal, a mobile terminal, astation, a subscriber station, a mobile station, a portable subscriberstation a subscriber station, a node, a device, an on-broad unit (OBU),or the like.

Meanwhile, the communications between the UEs 235 and 236 may beperformed based on the sidelink communication technique. The sidelinkcommunications may be performed based on a one-to-one scheme or aone-to-many scheme. When V2V communications are performed using thesidelink communication technique, the UE 235 may be the communicationnode located in the first vehicle 100 of FIG. 1 and the UE 236 may bethe communication node located in the second vehicle 110 of FIG. 1. WhenV2I communications are performed using the sidelink communicationtechnique, the UE 235 may be the communication node located in firstvehicle 100 of FIG. 1 and the UE 236 may be the communication nodelocated in the infrastructure 120 of FIG. 1. When V2P communications areperformed using the sidelink communication technique, the UE 235 may bethe communication node located in first vehicle 100 of FIG. 1 and the UE236 may be the communication node carried by the person 130 of FIG. 1.

The scenarios to which the sidelink communications are applied may beclassified as shown below in Table 1 according to the positions of theUEs (e.g., the UEs 235 and 236) participating in the sidelinkcommunications. For example, the scenario for the sidelinkcommunications between the UEs 235 and 236 shown in FIG. 2 may be asidelink communication scenario C.

TABLE 1 Sidelink Communication Scenario Position of UE 235 Position ofUE 236 A Out of coverage of Out of coverage of base station 210 basestation 210 B In coverage of Out of coverage of base station 210 basestation 210 C In coverage of In coverage of base station 210 basestation 210 D In coverage of In coverage of base station 210 other basestation

Meanwhile, a user plane protocol stack of the UEs (e.g., the UEs 235 and236) performing sidelink communications may be configured as follows.

FIG. 4 is a block diagram illustrating embodiments of a user planeprotocol stack of an UE performing sidelink communication.

As shown in FIG. 4, a left UE may be the UE 235 shown in FIG. 2 and aright UE may be the UE 236 shown in FIG. 2. The scenario for thesidelink communications between the UEs 235 and 236 may be one of thesidelink communication scenarios A through D of Table 1. The user planeprotocol stack of each of the UEs 235 and 236 may comprise a physical(PHY) layer, a medium access control (MAC) layer, a radio link control(RLC) layer, and a packet data convergence protocol (PDCP) layer.

The sidelink communications between the UEs 235 and 236 may be performedusing a PC5 interface (e.g., PC5-U interface). A layer-2 identifier (ID)(e.g., a source layer-2 ID, a destination layer-2 ID) may be used forthe sidelink communications and the layer 2-ID may be an ID configuredfor the V2X communications. Also, in the sidelink communications, ahybrid automatic repeat request (HARQ) feedback operation may besupported, and an RLC acknowledged mode (RLC AM) or an RLCunacknowledged mode (RLC UM) may be supported.

Meanwhile, a control plane protocol stack of the UEs (e.g., the UEs 235and 236) performing sidelink communications may be configured asfollows.

FIG. 5 is a block diagram illustrating a first embodiment of a controlplane protocol stack of an UE performing sidelink communication, andFIG. 6 is a block diagram illustrating a second embodiment of a controlplane protocol stack of an UE performing sidelink communication.

As shown in FIGS. 5 and 6, a left UE may be the UE 235 shown in FIG. 2and a right UE may be the UE 236 shown in FIG. 2. The scenario for thesidelink communications between the UEs 235 and 236 may be one of thesidelink communication scenarios A through D of Table 1. The controlplane protocol stack illustrated in FIG. 5 may be a control planeprotocol stack for transmission and reception of broadcast information(e.g., Physical Sidelink Broadcast Channel (PSBCH)).

The control plane protocol stack shown in FIG. 5 may include a PHYlayer, a MAC layer, an RLC layer, and a radio resource control (RRC)layer. The sidelink communications between the UEs 235 and 236 may beperformed using a PC5 interface (e.g., PC5-C interface). The controlplane protocol stack shown in FIG. 6 may be a control plane protocolstack for one-to-one sidelink communication. The control plane protocolstack shown in FIG. 6 may include a PHY layer, a MAC layer, an RLClayer, a PDCP layer, and a PC5 signaling protocol layer.

Meanwhile, channels used in the sidelink communications between the UEs235 and 236 may include a Physical Sidelink Shared Channel (PSSCH), aPhysical Sidelink Control Channel (PSCCH), a Physical Sidelink DiscoveryChannel (PSDCH), and/or a Physical Sidelink Broadcast Channel (PSBCH).The PSSCH may be used for transmitting and receiving sidelink data andmay be configured in the UE (e.g., UE 235 or 236) by a higher layersignaling. The PSCCH may be used for transmitting and receiving sidelinkcontrol information (SCI) and may also be configured in the UE (e.g., UE235 or 236) by a higher layer signaling.

The PSDCH may be used for a discovery procedure. For example, adiscovery signal may be transmitted over the PSDCH. The PSBCH may beused for transmitting and receiving broadcast information (e.g., systeminformation). Also, a demodulation reference signal (DM-RS), asynchronization signal, or the like may be used in the sidelinkcommunications between the UEs 235 and 236.

Meanwhile, a sidelink transmission mode (TM) may be classified intosidelink TMs 1 to 4 as shown below in Table 2.

TABLE 2 Sidelink TM Description 1 Transmission using resources scheduledby base station 2 UE autonomous transmission without scheduling of basestation 3 Transmission using resources scheduled by base station in V2Xcommunications 4 UE autonomous transmission without scheduling of basestation in V2X communications

When the sidelink TM 3 or 4 is supported, each of the UEs 235 and 236may perform sidelink communications using a resource pool configured bythe base station 210. The resource pool may be configured for each ofthe sidelink control information and the sidelink data.

The resource pool for the sidelink control information may be configuredbased on an RRC signaling procedure (e.g., a dedicated RRC signalingprocedure, a broadcast RRC signaling procedure). The resource pool usedfor reception of the sidelink control information may be configured by abroadcast RRC signaling procedure. When the sidelink TM 3 is supported,the resource pool used for transmission of the sidelink controlinformation may be configured by a dedicated RRC signaling procedure. Inthis case, the sidelink control information may be transmitted throughresources scheduled by the base station 210 within the resource poolconfigured by the dedicated RRC signaling procedure. When the sidelinkTM 4 is supported, the resource pool used for transmission of thesidelink control information may be configured by a dedicated RRCsignaling procedure or a broadcast RRC signaling procedure. In thiscase, the sidelink control information may be transmitted throughresources selected autonomously by the UE (e.g., UE 235 or 236) withinthe resource pool configured by the dedicated RRC signaling procedure orthe broadcast RRC signaling procedure.

When the sidelink TM 3 is supported, the resource pool for transmittingand receiving sidelink data may not be configured. In this case, thesidelink data may be transmitted and received through resourcesscheduled by the base station 210. When the sidelink TM 4 is supported,the resource pool for transmitting and receiving sidelink data may beconfigured by a dedicated RRC signaling procedure or a broadcast RRCsignaling procedure. In this case, the sidelink data may be transmittedand received through resources selected autonomously by the UE (e.g., UE235 or 236) within the resource pool configured by the dedicated RRCsignaling procedure or the broadcast RRC signaling procedure.

Hereinafter, methods for load distribution using a plurality of carriers(e.g., a plurality of channels) in the communication system (e.g., thecellular communication system) supporting V2X communications asdescribed above will be described. Even when a method (e.g.,transmission or reception of a signal) to be performed at a firstcommunication node among communication nodes is described, acorresponding second communication node may perform a method (e.g.,reception or transmission of the signal) corresponding to the methodperformed at the first communication node. That is, when an operation ofthe vehicle 100 is described, the corresponding vehicle 110 may performan operation corresponding to the operation of the vehicle 100.Conversely, when an operation of the vehicle 110 is described, thecorresponding vehicle 100 may perform an operation corresponding to theoperation of the vehicle 110. In the embodiments described below, theoperation of the vehicle may be the operation of the communication nodelocated in the vehicle.

In the communication system supporting V2X communications, the vehiclemay perform communications based on the CA scheme. For example, thevehicle may perform communications using a primary carrier and one ormore secondary carriers. The carrier used for the V2X communications maybe determined based on channel state information (e.g., Channel BusyRatio (CBR)). The CBR may indicate congestion, occupancy state, loadstate, etc. of the corresponding carrier (e.g., channel). In this case,the vehicle may measure the CBR in the carrier according to a periodicor specific event, and may transmit the measured CBR to the basestation. The base station may identify a channel congestion (e.g.,occupancy state, load state) based on the CBR measured by the vehicle,and determine resources (e.g., carrier, resource pool) to be allocatedto the vehicle based on the measured channel congestion.

When the sidelink TM 3 is used, the base station may configuretime-frequency resources used for data transmission and may inform thevehicle of information on the configured time-frequency resources (i.e.,scheduling information). Also, the base station may allocatetime-frequency resources based on a semi-persistent scheduling (SPS)scheme. For example, the base station may configure up to eight SPSconfigurations having different parameters, and may transmit an SPSconfiguration activation message or an SPS deactivation request messageto the vehicle through a signaling procedure.

The SPS configuration may be configured based on UE assistanceinformation received from the vehicle. The UE assistance information mayinclude traffic characteristic parameters, and the trafficcharacteristic parameters may include a set of preferred or expected SPSintervals, a timing offset associated with a subframe #0 within a systemframe of a system frame number (SFN) #0, a ProSe Per-Packet Priority(PPPP), a maximum Transport Block Size (TBS) according to a trafficpattern, or the like.

When the sidelink TM 4 is used, the base station may configure theresource pool used for data transmission and may inform the vehicle ofinformation on the configured resource pool. In this case, the vehiclemay select a time-frequency resource that is not used by othercommunication nodes through channel sensing in the resource pool, andmay perform communications using the selected time-frequency resource.For example, the time-frequency resource may be selected based on adistributed congestion control scheme. Also, the vehicle may adjusttransmission parameters (e.g., a maximum transmission power, a range ofretransmission counts per transport block (TB), etc.) based on the CBR,and perform communications using the adjusted transmission parameters.When the sidelink TM 4 is used, a vehicle located outside the coverageof the base station may also perform communications using time-frequencyresources in a resource pool pre-configured by the base station.

However, when the sidelink TM 3 and the SPS scheme are used, when a loadon the carrier on which the SPS configuration is activated increases,data of the vehicle (e.g., data having high reliability and low latencyrequirements, DENM, CAM, etc.) may not be successfully transmitted orreceived. Also, a transmission latency of the data may increase, andthus a requested quality of service (QoS) may not be satisfied. The loaddistribution methods to solve this problem may be as follows.

FIG. 7 is a sequence chart illustrating a first embodiment of a loaddistribution method using heterogeneous RATs.

As shown in FIG. 7, a communication system supporting V2X communicationsmay include a vehicle, a communication node equipped in the vehicle, afirst base station, a second base station, and the like. For example,the vehicle of FIG. 7 may be the vehicle 100 of FIG. 1, and thecommunication node of FIG. 7 may be the communication node located inthe vehicle 110 of FIG. 1, the communication node located in theinfrastructure 120, or the communication node carried by the person 130.Each of the first and second base stations in FIG. 7 may be a basestation belonging to the cellular communication system 140 of FIG. 1.Also, although each of the first and second base stations illustrativelyexists as a single base station in FIG. 7 and description below, theremay be one or more first base stations and one or more second basestations.

The first and second base stations may support different RATs. Forexample, when the first base station supports a 4G communicationtechnology, the second base station may support a 5G communicationtechnology. Alternatively, when the first base station supports a 5Gcommunication technology, the second base station may support a 4Gcommunication technology. The V2X communications supported by the firstand second base stations may be performed based on the sidelink TM 3 andthe SPS scheme. Also the vehicle, the communication node, and the firstand second base stations in FIG. 7 may support the sidelink TM 4 as wellas the sidelink TM 3.

The vehicle may perform V2X communications with the communication nodebased on the SPS configuration set by the second base station (i.e.,serving base station that is currently serving the vehicle) (S701).Here, the V2X communications may be performed using one or morecarriers. The vehicle may measure channel states (e.g., CBRs) for theone or more carriers on which the V2X communications are performed(S702). Also, the vehicle may measure channel states of all the carriersconfigured for the vehicle as well as the one or more carriers on whichthe V2X communications are performed. That is, the vehicle may measureCBRs for all the aggregated carriers (e.g., all carriers to which the CAscheme is applied). The CBR measurement may be performed periodically orwhen a specific event (e.g., a request from the second base station)occurs. The vehicle may compare the measured CBR with a predeterminedthreshold value and determine that an overload has occurred in thecorresponding carrier if the measured CBR is greater than or equal tothe predetermined threshold value.

Also, in the step S702, the vehicle may discover at least one adjacentbase station. The at least one adjacent base station may be a targetbase station to share the load of the second base station. For example,the vehicle may receive a synchronization signal (e.g., a PrimarySynchronization Signal (PSS) and a Secondary Synchronization Signal(SSS), or a Synchronization Signal (SS) block (SSB)) from the first basestation (i.e., the target base station), identify downlink timing of thefirst base station based on the synchronization signal, and receivesystem information of the first base station based on the downlinktiming. The vehicle may identify uplink timing of the first base stationby performing a random access procedure with the first base stationusing resources indicated by the system information.

When an overload occurs in the carrier configured by the second basestation and the first base station is discovered, the vehicle may changea SPS configuration (e.g., an original SPS configuration) used for theV2X communications in the step S701 (S703). However, when the SPSconfiguration used for the V2X communications (e.g., the V2Xcommunications supported by the second base station) in the step S710 isapplied equally to the V2X communications supported by the first basestation, the step S703 may be omitted.

In the step S703, the SPS configuration may be changed based on thenumber of adjacent base stations (e.g., target base stations) determinedin the step S702. The step S703 may be performed based on a SPSconfiguration change scheme 1, 2 or 3.

SPS Configuration Change Scheme 1

When a sum of the number of at least one serving base station (e.g., thenumber of the second base stations) and the number of at least onetarget base station (e.g., the number of the first base stations) is N,and a data transmission interval in the SPS configuration supported bythe at least one serving base station is T transmission time intervals(TTIs), the vehicle may set a data transmission interval to N×T TTIs ina new SPS configuration (i.e., a reconfigured SPS configuration) for theN base stations, and set an offset between data transmission intervalsof the N base stations to T TTIs. For example, when N is 2 and T is 5,the data transmission interval in each of two base stations (e.g.,serving base station and target base station) may be set to 10 TTIs, andan offset between data transmission intervals of the two base stationsmay be set to 5 TTIs. When a radio frame is composed of subframes 0 to9, the V2X communications supported by the serving base station may beperformed using the subframe 0, and the V2X communications supported bythe target base station may be performed using the subframe 5.

SPS Configuration Change Scheme 2

When a sum of the number of at least one serving base station (e.g., thenumber of the second base stations) and the number of at least onetarget base station (e.g., the number of the first base stations) is N,and a data transmission interval in the SPS configuration supported bythe at least one serving base station is T TTIs, the vehicle maymaintain the data transmission interval to be T TTIs in the N basestations, set an offset between data transmission intervals of the Nbase stations to M TTIs (M is an integer greater than or equal to 0),and set a size of data transmitted through each of the N base stationsto (a size of total data to be transmitted to the communication node)/N.That is, data of the same size may be transmitted in each of the N basestations.

For example, when N is 2, T is 5, M is 0, and the size of total datacorresponds to 10 TBs, the data transmission interval in each of twobase stations (e.g., serving base station and target base station) maybe set to 5 TTIs, an offset between data transmission intervals of thetwo base stations may be set to 0 TTI, and the size of data transmittedin each of the two base stations may correspond to 5 TBs.

SPS Configuration Change Scheme 3

When a sum of the number of at least one serving base station (e.g., thenumber of the second base stations) and the number of at least onetarget base station (e.g., the number of the first base stations) is N,and a data transmission interval in the SPS configuration supported bythe at least one serving base station is T TTIs, the vehicle maymaintain the data transmission interval to be T TTIs in the N basestations, set an offset between data transmission intervals of the Nbase stations to M TTIs (M is an integer greater than or equal to 0),and set the size of data transmitted through each of the N base stationsto be in inverse proportion to the CBR of each of the N base stations.That is, data can be distributed in consideration of channel congestionin each of the N base stations.

For example, when N is 2, T is 5, M is 0, the size of total datacorresponds to 10 TBs, the CBR of the serving base station is 80%, andthe CBR of the target base station is 20%, the data transmissioninterval in each of the two base stations may be set to 5 TTIs, anoffset between the data transmission intervals of the two base stationsmay be set to 0 TTI, the size of data transmitted through resourcesallocated by the serving base station may correspond to 2 TBs, and thesize of data transmitted through resources allocated by the target basestation may correspond to 8 TB s.

When the step S703 is completed, the vehicle may transmit an RRCconnection request message to the target base station (e.g., the firstbase station) to which the changed SPS configuration is to be applied(S704). The RRC connection request message may include an indicatorrequesting an RRC connection for performing V2X communications based onthe changed SPS configuration. The first base station may receive theRRC connection request message from the vehicle and confirm that an RRCconnection is requested for performing V2X communications according tothe changed SPS configuration based on the received RRC connectionrequest message. The first base station may transmit an RRC connectionsetup message to the vehicle in response to the RRC connection requestmessage (S705).

The vehicle may receive the RRC connection setup message from the firstbase station and may perform an RRC connection establishment procedurewith the first base station. When an RRC connection establishmentbetween the vehicle and the first base station is completed, the vehiclemay generate an RRC connection setup complete message including anidentifier of the serving base station (e.g., the second base station),the changed SPS configuration, and the like. When the SPS configurationchange scheme 1 is used, the RRC connection setup complete (e.g., thechanged SPS configuration) may include the data transmission interval(N×T), the offset between data transmission intervals (T), and the like.When the SPS configuration change scheme 2 is used, the RRC connectionsetup complete message may include the data transmission interval (T),the offset between data transmission intervals (M), the size of data(i.e., data of the same size is transmitted in each base station) whichcan be transmitted through resources allocated by the target basestation (e.g., the first base station), and the like. When the SPSconfiguration change scheme 3 is used, the RRC connection setup completemessage (e.g., the changed SPS configuration) may include the datatransmission interval (T), the offset between data transmissionintervals (M), the size of data (i.e., the size of data is inverselyproportional to the channel congestion of each base station) which canbe transmitted through resources allocated by the target base station(e.g., the first base station), and the like.

The vehicle may transmit the RRC connection setup complete message tothe first base station (S706). The first base station may receive theRRC connection setup complete message from the vehicle and may identifythe information included in the received RRC connection setup completemessage (e.g., the identifier of the serving base station (e.g., thesecond base station), the changed SPS configuration, the size of data,etc.). When the application of the changed SPS configuration is allowed,the first base station may transmit to the vehicle an RRC connectionreconfiguration message including an indicator indicating that theapplication of the changed SPS configuration is allowed (S707). Also, anRRC connection reconfiguration message (e.g., an RRC connectionreconfiguration message including the new SPS configuration (i.e., thechanged SPS configuration) may be transmitted to the communication nodeperforming V2X communications with the vehicle. The vehicle may receivethe RRC connection reconfiguration message from the first base stationand confirm that the application of the changed SPS configuration isallowed in the first base station based on the received RRC connectionreconfiguration message.

Also, the vehicle may generate UE assistance information including theidentifier of the target base station (e.g., the first base station) towhich the changed SPS configuration is applied, the changed SPSconfiguration, and the like, and transmit the generated UE assistanceinformation to the second base station (S708). Alternatively, in thestep S708, sidelink UE information may be used instead of the UEassistance information. When the SPS configuration change scheme 1 isused, the UE assistance information (e.g., the changed SPSconfiguration) may include the data transmission interval (N×T), theoffset between data transmission intervals (T), and the like. When theSPS configuration change scheme 2 is used, the UE assistance informationmay include the data transmission interval (T), the offset between datatransmission intervals (M), the size of data (e.g., the size of data isthe same in the base stations) which can be transmitted throughresources allocated by the serving base station (e.g., the second basestation), and the like. When the SPS configuration change scheme 3 isused, the UE assistance information (e.g., the changed SPSconfiguration) may include the data transmission interval (T), theoffset between data transmission intervals (M), the size of data (e.g.,the size of data is inversely proportional to the channel congestion ofeach base station) which can be transmitted through resources allocatedby the serving base station (e.g., the second base station), and thelike.

The second base station may receive the UE assistance information fromthe vehicle and may identify the information included in the received UEassistance information (e.g., the identifier of the target base station(e.g., the first base station), the changed SPS configuration, and thelike). The second base station may schedule resources for V2Xcommunications based on the information included in the UE assistanceinformation. That is, the second base station may identify resourcesthat are not scheduled by the SPS scheme according to the changed SPSconfiguration, and schedule resources for V2X communications of othervehicles using the identified resources.

Also, the base station may transmit to the vehicle an SPS configurationactivation message indicating activation of the changed SPSconfiguration indicated by the UE assistance information (S709). The SPSconfiguration activation message may also be transmitted to thecommunication node. The vehicle may receive the SPS configurationactivation message from the base station, and may perform V2Xcommunications with the communication node using resources allocated bythe first and second base stations according to the changed SPSconfiguration (S710). Alternatively, the vehicle may perform V2Xcommunications with the communication node using resources allocated bythe first and second base stations according to the changed SPSconfiguration without receiving the SPS configuration active messageafter transmission of the UE assistance information (S710).

Also, the changed SPS configuration (e.g., information on at least oneadjacent base stations (i.e., target base station information;hereinafter, “adjacent base station information”), the data transmissioninterval, the offset between data transmission intervals, and the sizeof data that can be transmitted by each base station) used in the stepS710 for the V2X communications between the vehicle and thecommunication node may be transmitted from the vehicle to thecommunication node before the step S710. For example, the vehicle maygenerate an SCI including the changed SPS configuration. When a SCIformat 1 is used, the SCI format 1 may further include the changed SPSconfiguration, an application flag, and the like in addition to theexisting information. In this case, the SCI format 1 may includeinformation elements (IEs) shown below in Table 3.

TABLE 3 IE Description MCS Modulation and Coding Scheme (MCS) used forV2X communications Priority Priority of Transport Block (TB), which isconfigured by a higher layer signaling Time Gap Time gap between initialtransmission and retransmission Frequency resource positions of initialtransmission and retransmission Resource Resource reservation intervalin V2X communications reservation interval Changed SPS Information onadjacent base stations (identifiers of adjacent base configurationstations, the number of adjacent base stations) Data transmissioninterval Offset between data transmission intervals Size of data whichcan be transmitted by each base station Application flag Informationindicating a time at which the changed SPS configuration is applied

The application flag may be set to 0 or 1. The application flag set to 0may indicate that the changed SPS configuration indicated by the SCI isapplied after transmission of the corresponding SCI. The applicationflag set to 1 may indicate that the changed SPS configuration indicatedby the SCI is applied from transmission of the corresponding SCI.Alternatively, a new SCI format may be defined that includes the changedSPS configuration and the application flag, and the vehicle may use thenew SCI format to inform the communication node of the changed SPSconfiguration.

The vehicle may transmit the SCI (or, SCI+data) to the communicationnode. The communication node may receive the SCI from the vehicle,identify the changed SPS configuration included in the SCI, and identifya time point at which the changed SPS configuration is applied based onthe application flag included in the SCI. Therefore, in the step S710,the vehicle and the communication node may perform V2X communicationsusing the changed SPS configuration at the time indicated by theapplication flag.

FIG. 8 is a sequence chart illustrating a second embodiment of a loaddistribution method using heterogeneous RATs.

As shown in FIG. 8, a communication system supporting V2X communicationsmay include a vehicle (e.g., a communication node located in thevehicle), a communication node, a first base station, a second basestation, and the like. For example, the vehicle of FIG. 8 may be thevehicle 100 of FIG. 1, and the communication node of FIG. 8 may be thecommunication node located in the vehicle 110 of FIG. 1, thecommunication node located in the infrastructure 120, or thecommunication node carried by the person 130. Each of the first andsecond base stations in FIG. 8 may be a base station belonging to thecellular communication system 140 of FIG. 1. Also, although each of thefirst and second base stations illustratively exists as a single basestation in FIG. 8 and description below, there may be one or more firstbase stations and one or more second base stations.

The first and second base stations may support different RATs. Forexample, when the first base station supports a 4G communicationtechnology, the second base station may support a 5G communicationtechnology. Alternatively, when the first base station supports a 5Gcommunication technology, the second base station may support a 4Gcommunication technology. The V2X communications supported by the firstand second base stations may be performed based on the sidelink TM 3 andthe SPS scheme. Also the vehicle, the communication node, and the firstand second base stations in FIG. 8 may support the sidelink TM 4 as wellas the sidelink TM 3.

The vehicle may perform V2X communications with the communication nodebased on the SPS configuration set by the second base station (e.g.,serving base station that is currently serving the vehicle) (S801).Here, the V2X communications may be performed using one or morecarriers. The vehicle may measure channel states (e.g., CBRs) for theone or more carriers on which the V2X communications are performed(S802). Also, the vehicle may measure channel states of all the carriersconfigured for the vehicle as well as the one or more carriers on whichthe V2X communications are performed. That is, the vehicle may measureCBRs for all the aggregated carriers (e.g., all carriers to which the CAscheme is applied). The CBR measurement may be performed periodically orwhen a specific event (e.g., a request from the second base station)occurs. The vehicle may compare the measured CBR with a predeterminedthreshold value and determine that an overload has occurred in thecarrier if the measured CBR is greater than or equal to thepredetermined threshold value.

Also, in the step S802, the vehicle may discover at least one adjacentbase station. The at least one adjacent base station may be a targetbase station to share the load of the second base station. For example,the vehicle may receive a synchronization signal (e.g., a PrimarySynchronization Signal (PSS) and a Secondary Synchronization Signal(SSS), or a Synchronization Signal (SS) block (SSB)) from the first basestation (i.e., the target base station), identify downlink timing of thefirst base station based on the synchronization signal, and receivesystem information of the first base station based on the downlinktiming. The vehicle may identify uplink timing of the first base stationby performing a random access procedure with the first base stationusing resources indicated by the system information. Also, the vehiclemay perform an RRC connection establishment procedure with thediscovered first base station.

When an overload occurs in the carrier configured by the second basestation and the first base station is discovered, the vehicle may changea SPS configuration (e.g., an original SPS configuration) used for theV2X communications in the step S801 (S803). However, when the SPSconfiguration used for the V2X communications (e.g., the V2Xcommunications supported by the second base station) in the step S810 isapplied equally to the V2X communications supported by the first basestation, the step S803 may be omitted.

In the step S803, the SPS configuration may be changed based on thenumber of adjacent base stations (e.g., target base stations) determinedin the step S802. The step S803 may be performed based on a SPSconfiguration change scheme 1, 2 or 3 described in the embodiment ofFIG. 7. When the step S803 is completed, the vehicle may generate UEassistance information including an SPS permit indicator, the identifierof the serving base station (e.g., the second base station), the changedSPS configuration, and the like, and transmit the generated UEassistance information to the first base station (S804).

The SPS permit indicator may request the changed SPS configuration to beapplied to the first base station. When the SPS configuration changescheme 1 is used, the UE assistance information (e.g., the changed SPSconfiguration) may include information on the data transmission interval(N×T), the offset between data transmission intervals (T), and the like.When the SPS configuration change scheme 2 is used, the UE assistanceinformation (e.g., the changed SPS configuration) may includeinformation on the data transmission interval (T), the offset betweendata transmission intervals (M), the size of data (i.e., the size ofdata is the same in all base stations) to be transmitted throughresources allocated by the target base station (e.g., the first basestation), and the like. When the SPS configuration change scheme 3 isused, the UE assistance information (e.g., the changed SPSconfiguration) may include information on the data transmission interval(T), the offset between data transmission intervals (M), the size ofdata (i.e., the size of data is inversely proportional to the channelcongestion of each base station) to be transmitted through resourcesallocated by the target base station (e.g. the first base station), andthe like.

The first base station may receive the UE assistance information fromthe vehicle, and identify information indicated by the received UEassistance information (e.g., the SPS permit indicator, the identifierof the serving base station (e.g., the second base station), the changedSPS configuration, the size of data, etc.). When the application of thechanged SPS configuration is allowed, the first base station maytransmit an RRC connection reconfiguration message to the vehicle byincluding an indicator indicating that the application of the changedSPS configuration is allowed in the RRC connection reconfigurationmessage (S805). Also, an RRC connection reconfiguration message (e.g.,an RRC connection reconfiguration message including the new SPSconfiguration (i.e., the changed SPS configuration)) may be transmittedto the communication node performing V2X communications with thevehicle. The vehicle may receive the RRC connection reconfigurationmessage from the first base station and identify that the application ofthe changed SPS configuration is allowed in the first base station basedon the received RRC connection reconfiguration message.

Also, the vehicle may generate UE assistance information including theidentifier of the target base station (e.g., the first base station) towhich the changed SPS configuration is applied, the changed SPSconfiguration, etc., and transmit the generated UE assistanceinformation to the second base station (S806). Alternatively, in thestep S806, sidelink UE information may be used instead of the UEassistance information. When the SPS configuration change scheme 1 isused, the UE assistance information (e.g., the changed SPSconfiguration) may include information on the data transmission interval(N×T), the offset between data transmission intervals (T), and the like.When the SPS configuration change scheme 2 is used, the UE assistanceinformation (e.g., the changed SPS configuration) may includeinformation on the data transmission interval (T), the offset betweendata transmission intervals (M), the size of data (i.e., the size ofdata is the same in all base stations) to be transmitted throughresources allocated by the serving base station (e.g., the second basestation), and the like. When the SPS configuration change scheme 3 isused, the UE assistance information (e.g., the changed SPSconfiguration) may include information on the data transmission interval(T), the offset between data transmission intervals (M), the size ofdata (i.e., the size of data is inversely proportional to the channelcongestion of each base station) to be transmitted through resourcesallocated by the serving base station (e.g., the second base station),and the like.

The second base station may receive the UE assistance information fromthe vehicle, and identify information indicated by the received UEassistance information (e.g., the identifier of the target base station(e.g., the first base station), the changed SPS configuration, etc.).The second base station may schedule resources for V2X communicationsbased on the information indicated by the UE assistance information.That is, the second base station may identify resources that are notscheduled by the SPS according to the changed SPS configuration, and mayschedule resources for V2X communication of other vehicles using theidentified resources.

Also, the base station may transmit, to the vehicle, an SPSconfiguration activation message indicating activation of the changedSPS configuration indicated by the UE assistance information (S807). TheSPS configuration activation message may also be transmitted to thecommunication node. The vehicle may receive the SPS configurationactivation message from the base station and may perform V2Xcommunications with the communication node using the resources allocatedby the first base station and the second base station according to thechanged SPS configuration (S808). Alternatively, the vehicle may performV2X communications with the communication node using the resourcesallocated by the first base station and the second base stationaccording to the changed SPS configuration without receiving the SPSconfiguration activation message after transmission of the UE assistanceinformation (S808).

Also, the changed SPS configuration used in the step S808 for the V2Xcommunications between the vehicle and the communication node (e.g., theadjacent base station information, the data transmission interval, theoffset between data transmission intervals, the size of data which canbe transmitted through each base station) may be transmitted from thevehicle to the communication node before the step S808. For example, thevehicle may generate a SCI including information elements described inTable 3 (e.g., the changed SPS configuration, the application flag,etc.), and transmit the SCI (or, SCI+data) to the communication node.The communication node may receive the SCI from the vehicle, identifythe changed SPS configuration included in the SCI, and identify the timepoint at which the changed SPS configuration is applied based on theapplication flag included in the SCI. Therefore, in the step S808, thevehicle and the communication node may perform V2X communications usingthe changed SPS configuration at the time indicated by the applicationflag.

FIG. 9 is a sequence chart illustrating a third embodiment of a loaddistribution method using heterogeneous RATs.

As shown in FIG. 9, a communication system supporting V2X communicationsmay include a vehicle, a communication node equipped in the vehicle, afirst base station, a second base station, and the like. For example,the vehicle of FIG. 9 may be the vehicle 100 of FIG. 1, and thecommunication node of FIG. 9 may be the communication node located inthe vehicle 110 of FIG. 1, the communication node located in theinfrastructure 120, or the communication node carried by the person 130.Each of the first and second base stations in FIG. 9 may be a basestation belonging to the cellular communication system 140 of FIG. 1.Also, although each of the first and second base stations illustrativelyexists as a single base station in FIG. 9 and description below, theremay be one or more first base stations and one or more second basestations.

The first and second base stations may support different RATs. Forexample, when the first base station supports a 4G communicationtechnology, the second base station may support a 5G communicationtechnology. Alternatively, when the first base station supports a 5Gcommunication technology, the second base station may support a 4Gcommunication technology. The V2X communications supported by the firstand second base stations may be performed based on the sidelink TM 3 andthe SPS scheme. Also the vehicle, the communication node, and the firstand second base stations in FIG. 9 may support the sidelink TM 4 as wellas the sidelink TM 3.

The vehicle may perform V2X communications with the communication nodebased on the SPS configuration set by the second base station (e.g.,serving base station that is currently serving the vehicle) (S901).Here, the V2X communications may be performed using one or morecarriers. The vehicle may measure channel states (e.g., CBRs) for theone or more carriers on which the V2X communications are performed(S902). Also, the vehicle may measure channel states of all the carriersconfigured for the vehicle as well as the one or more carriers on whichthe V2X communications are performed. That is, the vehicle may measureCBRs for all the aggregated carriers (e.g., all carriers to which the CAscheme is applied). The CBR measurement may be performed periodically orwhen a specific event (e.g., a request from the second base station)occurs. The vehicle may compare the measured CBR with a predeterminedthreshold value and determine that an overload has occurred in thecarrier if the measured CBR is greater than or equal to thepredetermined threshold value.

Also, in the step S902, the vehicle may discover at least one adjacentbase station. The at least one adjacent base station may be a targetbase station to share the load of the second base station. For example,the vehicle may receive a synchronization signal (e.g., PSS and SSS, orSSB) from the first base station (i.e., the target base station),identify downlink timing of the first base station based on thesynchronization signal, and receive system information of the first basestation based on the downlink timing. The vehicle may identify uplinktiming of the first base station by performing a random access procedurewith the first base station using resources indicated by the systeminformation.

When an overload occurs in the carrier configured by the second basestation and the first base station is discovered, the vehicle maygenerate UE assistance information including a load distributionindicator, the identifier of the target base station (e.g., the firstbase station), etc., and transmit the generated UE assistanceinformation to the second base station (S903). Alternatively, in thestep S903, sidelink UE information may be used instead of the UEassistance information. The load distribution indicator may request loaddistribution through the target base station indicated by the UEassistance information. The second base station may receive the UEassistance information from the vehicle and identify the informationincluded in the received UE assistance information (e.g., the loaddistribution indicator, the identifier of the target base station (e.g.,the first base station)).

That is, the second base station may confirm that the load distributionthrough the first base station is requested based on the UE assistanceinformation. In this case, the second base station may change the SPSconfiguration (e.g., the original SPS configuration) used for V2Xcommunications in step S901 (S904). However, when the SPS configurationused in the step S901 for the V2X communications (e.g., V2Xcommunications supported by the second base station) is applied to theV2X communication supported by the first base station, the step S904 maybe omitted.

In the step S904, the SPS configuration (e.g., SPS parameters) may bechanged based on the number of adjacent base stations (e.g., target basestations) determined in the step S902. The step S904 may be performedbased on the SPS configuration change scheme 1, 2 or 3 described in theembodiment of FIG. 7. In the embodiment of FIG. 7, the SPS configurationchange scheme 1, 2 or 3 is performed by the vehicle. However, in theembodiment of FIG. 9, the SPS configuration change scheme 1, 2 or 3 maybe performed by the base station instead of the vehicle. That is, theoperation of the base station performing the SPS configuration changescheme 1, 2 or 3 in the embodiment of FIG. 9 may be the same as theoperation of the vehicle performing the SPS configuration change scheme1, 2 or 3 in the embodiment of FIG. 7.

When the step S904 is completed, the second base station may transmit anRRC connection reconfiguration message including the changed SPSconfiguration to the vehicle (S905). The RRC connection reconfigurationmessage may also be transmitted to the communication node performing V2Xcommunications with the vehicle. When the SPS configuration changescheme 1 is used, the RRC connection reconfiguration message (e.g., thechanged SPS configuration) may include information on the datatransmission interval (N×T), the offset between data transmissionintervals (T), and the like. When the SPS configuration change scheme 2is used, the RRC connection reconfiguration message (e.g., the changedSPS configuration) may include information on the data transmissioninterval (T), the offset between data transmission intervals (M), thesize of data (i.e., the size of data is the same in all base stations)to be transmitted through resources allocated by the target base station(e.g., the first base station), and the like. When the SPS configurationchange scheme 3 is used, the RRC connection reconfiguration message(e.g., the changed SPS configuration) may include information on thedata transmission interval (T), the offset between data transmissionintervals (M), the size of data (i.e., the size of data is inverselyproportional to the channel congestion of each base station) to betransmitted through resources allocated by the target base station (e.g.the first base station), and the like. The vehicle may receive the RRCconnection reconfiguration message from the second base station, andidentify the changed SPS configuration included in the received RRCconnection reconfiguration message.

When the step S905 is completed, the vehicle may transmit an RRCconnection request message to the target base station (e.g., the firstbase station) to which the changed SPS configuration is to be applied(S906). The RRC connection request message may include an indicatorrequesting an RRC connection for performing V2X communications based onthe changed SPS configuration. The first base station may receive theRRC connection request message from the vehicle and confirm that an RRCconnection is requested for performing V2X communications according tothe changed SPS configuration based on the received RRC connectionrequest message. The first base station may transmit an RRC connectionsetup message to the vehicle in response to the RRC connection requestmessage (S907).

The vehicle may receive the RRC connection setup message from the firstbase station and may perform an RRC connection establishment procedurewith the first base station. When an RRC connection establishmentbetween the vehicle and the first base station is completed, the vehiclemay generate an RRC connection complete message including an identifierof the serving base station (e.g., the second base station), the changedSPS configuration, and the like. When the SPS configuration changescheme 1 is used, the RRC connection setup complete (e.g., the changedSPS configuration) may include the data transmission interval (N×T), theoffset between data transmission intervals (T), and the like. When theSPS configuration change scheme 2 is used, the RRC connection setupcomplete message (e.g., the changed SPS configuration) may include thedata transmission interval (T), the offset between data transmissionintervals (M), the size of data (i.e., the size of data is the same inall base stations) which can be transmitted through resources allocatedby the target base station (e.g., the first base station), and the like.When the SPS configuration change scheme 3 is used, the RRC connectionsetup complete message (e.g., the changed SPS configuration) may includethe data transmission interval (T), the offset between data transmissionintervals (M), the size of data (i.e., the size of data is inverselyproportional to the channel congestion of each base station) which canbe transmitted through resources allocated by the target base station(e.g., the first base station), and the like.

The vehicle may transmit an RRC connection setup complete message to thefirst base station (S908). The first base station may receive the RRCconnection setup complete message from the vehicle and may identify theinformation included in the received RRC connection setup completemessage (e.g., the identifier of the serving base station (e.g., thesecond base station), the changed SPS configuration, the size of data,etc.). When the application of the changed SPS configuration is allowed,the first base station may transmit to the vehicle an RRC connectionreconfiguration message including an indicator indicating that theapplication of the changed SPS configuration is allowed (S909). Also, anRRC connection reconfiguration message (e.g., an RRC connectionreconfiguration message including a new SPS configuration (i.e., thechanged SPS configuration) may be transmitted to the communication nodeperforming V2X communications with the vehicle. The vehicle may receivethe RRC connection reconfiguration message from the first base stationand confirm that the application of the changed SPS configuration isallowed in the first base station based on the received RRC connectionreconfiguration message (S910).

Also, the changed SPS configuration used in the step S910 for the V2Xcommunications between the vehicle and the communication node (e.g.,information on adjacent base stations, the data transmission interval,the offset between data transmission intervals, the size of data whichcan be transmitted through each base station) may be transmitted fromthe vehicle to the communication node before the step S910. For example,the vehicle may generate a SCI including information elements describedin Table 3 (e.g., the changed SPS configuration, the application flag,etc.), and transmit the SCI (or, SCI+data) to the communication node.The communication node may receive the SCI from the vehicle, identifythe changed SPS configuration included in the SCI, and identify the timepoint at which the changed SPS configuration is applied based on theapplication flag included in the SCI. Therefore, in the step S910, thevehicle and the communication node may perform V2X communications usingthe changed SPS configuration at the time indicated by the applicationflag.

FIG. 10 is a sequence chart illustrating a fourth embodiment of a loaddistribution method using heterogeneous RATs.

As shown in FIG. 10, a communication system supporting V2Xcommunications may include a vehicle, a communication node equipped inthe vehicle, a first base station, a second base station, and the like.For example, the vehicle of FIG. 10 may be the vehicle 100 of FIG. 1,and the communication node of FIG. 10 may be the communication nodelocated in the vehicle 110 of FIG. 1, the communication node located inthe infrastructure 120, or the communication node carried by the person130. Each of the first and second base stations in FIG. 10 may be a basestation belonging to the cellular communication system 140 of FIG. 1.Also, although each of the first and second base stations illustrativelyexists as a single base station in FIG. 10 and description below, theremay be one or more first base stations and one or more second basestations.

The first and second base stations may support different RATs. Forexample, when the first base station supports a 4G communicationtechnology, the second base station may support a 5G communicationtechnology. Alternatively, when the first base station supports a 5Gcommunication technology, the second base station may support a 4Gcommunication technology. The V2X communications supported by the firstand second base stations may be performed based on the sidelink TM 3 andthe SPS scheme. Also the vehicle, the communication node, and the firstand second base stations in FIG. 10 may support the sidelink TM 4 aswell as the sidelink TM 3.

The vehicle may perform V2X communications with the communication nodebased on the SPS configuration set by the second base station (e.g.,serving base station that is currently serving the vehicle) (S1001).Here, the V2X communications may be performed using one or morecarriers. The vehicle may measure channel states (e.g., CBRs) for theone or more carriers on which the V2X communications are performed(S1002). Also, the vehicle may measure channel states of all thecarriers configured for the vehicle as well as the one or more carrierson which the V2X communications are performed. That is, the vehicle maymeasure CBRs for all the aggregated carriers (e.g., all carriers towhich the CA scheme is applied). The CBR measurement may be performedperiodically or when a specific event (e.g., a request from the secondbase station) occurs. The vehicle may compare the measured CBR with apredetermined threshold value and determine that an overload hasoccurred in the carrier if the measured CBR is greater than or equal tothe predetermined threshold value.

Also, in the step S1002, the vehicle may discover at least one adjacentbase station. The at least one adjacent base station may be a targetbase station to share the load of the second base station. For example,the vehicle may receive a synchronization signal (e.g., PSS and SSS, orSSB) from the first base station (i.e., the target base station),identify downlink timing of the first base station based on thesynchronization signal, and receive system information of the first basestation based on the downlink timing. The vehicle may identify uplinktiming of the first base station by performing a random access procedurewith the first base station using resources indicated by the systeminformation.

When an overload occurs in the carrier configured by the second basestation and the first base station is discovered, the vehicle maygenerate UE assistance information including a load distributionindicator, the identifier of the target base station (e.g., the firstbase station), etc., and transmit the generated UE assistanceinformation to the second base station (S1003). Alternatively, in thestep S1003, sidelink UE information may be used instead of the UEassistance information. The load distribution indicator may request loaddistribution through the target base station indicated by the UEassistance information. The second base station may receive the UEassistance information from the vehicle and identify the informationincluded in the received UE assistance information (e.g., the loaddistribution indicator, the identifier of the target base station (e.g.,the first base station)).

That is, the second base station may confirm that the load distributionthrough the first base station is requested based on the UE assistanceinformation. In this case, the second base station may change the SPSconfiguration (e.g., the original SPS configuration) used for V2Xcommunications in step S1001 (S1004). However, when the SPSconfiguration used in the step S1001 for the V2X communications (e.g.,V2X communications controlled by the second base station) is applied tothe V2X communication controlled by the first base station, the stepS1004 may be omitted.

In the step S1004, the SPS configuration (e.g., SPS parameters) may bechanged based on the number of adjacent base stations (e.g., target basestations) determined in the step S1002. The step S1004 may be performedbased on the SPS configuration change scheme 1, 2 or 3 described in theembodiment of FIG. 7. In the embodiment of FIG. 7, the SPS configurationchange scheme 1, 2 or 3 are performed by the vehicle. However, in theembodiment of FIG. 10, the SPS configuration change scheme 1, 2 or 3 maybe performed by the base station instead of the vehicle. That is, theoperation of the base station performing the SPS configuration changescheme 1, 2 or 3 in the embodiment of FIG. 10 may be the same as theoperation of the vehicle performing the SPS configuration change scheme1, 2 or 3 in the embodiment of FIG. 7.

When the step S1004 is completed, the second base station may transmitan RRC connection reconfiguration message including the changed SPSconfiguration to the vehicle (S1005). The RRC connection reconfigurationmessage may also be transmitted to the communication node performing V2Xcommunications with the vehicle. When the SPS configuration changescheme 1 is used, the RRC connection reconfiguration message (e.g., thechanged SPS configuration) may include information on the datatransmission interval (N×T), the offset between data transmissionintervals (T), and the like. When the SPS configuration change scheme 2is used, the RRC connection reconfiguration message (e.g., the changedSPS configuration) may include information on the data transmissioninterval (T), the offset between data transmission intervals (M), thesize of data (i.e., the size of data is the same in all base stations)to be transmitted through a resource allocated by the target basestation (e.g., the first base station), and the like. When the SPSconfiguration change scheme 3 is used, the RRC connectionreconfiguration message (e.g., the changed SPS configuration) mayinclude information on the data transmission interval (T), the offsetbetween data transmission intervals (M), the size of data (i.e., thesize of data is inversely proportional to the channel congestion of eachbase station) to be transmitted through a resource allocated by thetarget base station (e.g. the first base station), and the like. Thevehicle may receive the RRC connection reconfiguration message from thesecond base station, and identify the changed SPS configuration includedin the received RRC connection reconfiguration message.

When the step S1005 is completed, the vehicle may generate UE assistanceinformation including an SPS permit indicator, the identifier of theserving base station (e.g., the second base station), the changed SPSconfiguration, and the like, and transmit the generated UE assistanceinformation to the first base station (S1006). The SPS permit indicatormay request the changed SPS configuration to be applied to the firstbase station. When the SPS configuration change scheme 1 is used, the UEassistance information (e.g., the changed SPS configuration) may includeinformation on the data transmission interval (N×T), the offset betweendata transmission intervals (T), and the like. When the SPSconfiguration change scheme 2 is used, the UE assistance information(e.g., the changed SPS configuration) may include information on thedata transmission interval (T), the offset between data transmissionintervals (M), the size of data (i.e., the size of data is the same inall base stations) to be transmitted through a resource allocated by thetarget base station (e.g., the first base station), and the like. Whenthe SPS configuration change scheme 3 is used, the UE assistanceinformation (e.g., the changed SPS configuration) may includeinformation on the data transmission interval (T), the offset betweendata transmission intervals (M), the size of data (i.e., the size ofdata is inversely proportional to the channel congestion of each basestation) to be transmitted through a resource allocated by the targetbase station (e.g. the first base station), and the like.

The first base station may receive the UE assistance information fromthe vehicle, and identify information indicated by the received UEassistance information (e.g., the SPS permit indicator, the identifierof the serving base station (e.g., the second base station), the changedSPS configuration, the size of data, etc.). When the application of thechanged SPS configuration is allowed, the first base station maytransmit an RRC connection reconfiguration message to the vehicle byincluding an indicator indicating that the application of the changedSPS configuration is allowed in the RRC connection reconfigurationmessage (S1007). Also, the RRC connection reconfiguration message (e.g.,an RRC connection reconfiguration message including the new SPSconfiguration (i.e., the changed SPS configuration) may be transmittedto the communication node performing V2X communications with thevehicle. The vehicle may receive the RRC connection reconfigurationmessage from the first base station and identify that the application ofthe changed SPS configuration is allowed in the first base station basedon the received RRC connection reconfiguration message. Then, thevehicle may perform V2X communications with the communication node usingresources allocated by the first base station and the second basestation according to the changed SPS configuration (S1008).

Also, the changed SPS configuration used in the step S1008 for the V2Xcommunications between the vehicle and the communication node (e.g.,information on adjacent base stations, the data transmission interval,the offset between data transmission intervals, the size of data whichcan be transmitted through each base station) may be transmitted fromthe vehicle to the communication node before the step S1008. Forexample, the vehicle may generate a SCI including information elementsdescribed in Table 3 (e.g., the changed SPS configuration, theapplication flag, etc.), and transmit the SCI (or, the SCI+data) to thecommunication node. The communication node may receive the SCI from thevehicle, identify the changed SPS configuration included in the SCI, andidentify the time point at which the changed SPS configuration isapplied based on the application flag included in the SCI. Therefore, inthe step S1008, the vehicle and the communication node may perform V2Xcommunications using the changed SPS configuration at the time indicatedby the application flag.

The embodiments of the present disclosure may be implemented as programinstructions executable by a variety of computers and recorded on acomputer readable medium. The computer readable medium may include aprogram instruction, a data file, a data structure, or a combinationthereof. The program instructions recorded on the computer readablemedium may be designed and configured specifically for the presentdisclosure or can be publicly known and available to those who areskilled in the field of computer software.

Examples of the computer readable medium may include a hardware devicesuch as ROM, RAM, and flash memory, which are specifically configured tostore and execute the program instructions. Examples of the programinstructions include machine codes made by, for example, a compiler, aswell as high-level language codes executable by a computer, using aninterpreter. The above exemplary hardware device can be configured tooperate as at least one software module in order to perform theembodiments of the present disclosure, and vice versa.

While the embodiments of the present disclosure and their advantageshave been described in detail, it should be understood that variouschanges, substitutions and alterations may be made herein withoutdeparting from the scope of the present disclosure.

What is claimed is:
 1. A first communication node located in a vehicle,in a communication system supporting Vehicle-to-Everything (V2X)communication, the first communication node comprising: processor;transceiver transmitting and receiving a signal according to control ofthe processor; and memory storing one or more instructions which areexecuted by the processor; wherein the one or more instructions areconfigured to: perform V2X communication with a second communicationnode using an original resource according to an original Semi-PersistentScheduling (SPS) configuration set by a serving base station; when acongestion level in the original resource is greater than or equal to apredetermined threshold and at least one target base station supportingthe V2X communication is discovered, generate a new SPS configuration tobe applied to the serving base station and the at least one target basestation by changing the original SPS configuration; perform a messagetransmission and reception procedure with the at least one target basestation for delivery of the new SPS configuration; and perform the V2Xcommunication with the second communication node using a first resourcescheduled by the serving base station based on the new SPS configurationand a second resource scheduled by the at least one target base stationbased on the new SPS configuration.
 2. The first communication nodeaccording to claim 1, wherein, in the message transmission and receptionprocedure, the one or more instructions are configured to: transmit, tothe at least one target base station, a radio resource control (RRC)connection request message requesting a connection for applying the newSPS configuration; receive an RRC connection setup message from the atleast one target base station, the RRC connection setup message being aresponse to the RRC connection request message; transmit an RRCconnection setup complete message including an identifier of the servingbase station and the new SPS configuration to the at least one targetbase station when a connection establishment between the firstcommunication node and the at least one target base station iscompleted; and receive, from the at least one target base station, anRRC connection reconfiguration message indicating an application of thenew SPS configuration.
 3. The first communication node according toclaim 1, wherein, in the message transmission and reception procedure,the one or more instructions are configured to: transmit, to the atleast one target base station, user equipment (UE) assistanceinformation including an indicator requesting an application of the newSPS configuration, an identifier of the serving base station, and thenew SPS configuration; and receive, from the at least one target basestation, an RRC connection reconfiguration message indicating theapplication of the new SPS configuration.
 4. The first communicationnode according to claim 1, wherein the one or more instructions arefurther configured to: transmit, to the serving base station, UEassistance information including at least one identifier of the at leastone target base station and the new SPS configuration.
 5. The firstcommunication node according to claim 1, wherein the V2X communicationusing the first resource and the second resource based on the new SPSconfiguration are performed when a message requesting application of thenew SPS configuration is received from the serving base station and theat least one target base station.
 6. The first communication nodeaccording to claim 1, wherein a radio access technology (RAT) supportedby the serving base station is different from a RAT supported by the atleast one target base station.
 7. The first communication node accordingto claim 1, wherein, when a sum of a number of serving base stations anda number of the at least one target base station is N and a transmissioninterval of the original SPS configuration is T transmission timeintervals (TTIs), a transmission interval of the new SPS configurationis set to N×T TTIs, N is an integer greater than or equal to 2, and T isan integer greater than or equal to
 1. 8. The first communication nodeaccording to claim 7, wherein an offset between transmission intervalsof the N base stations is set to T TTIs in the new SPS configuration. 9.The first communication node according to claim 1, wherein, when a sumof a number of serving base stations and a number of the at least onetarget base station is N and a transmission interval of the original SPSconfiguration is T TTIs, a transmission interval of the new SPSconfiguration is set to T TTIs, a size of data to be transmitted througheach of the N base stations in the new SPS configuration equals (a sizeof total data to be transmitted to the second communication node)/N, Nis an integer greater than or equal to 2, and T is an integer greaterthan or equal to
 1. 10. The first communication node according to claim1, wherein, when a sum of a number of serving base stations and a numberof the at least one target base station is N and a transmission intervalof the original SPS configuration is T TTIs, a transmission interval ofthe new SPS configuration is set to T TTIs, a size of data to betransmitted through each of the N base stations in the new SPSconfiguration is inversely proportional to a channel congestion of eachof the N base stations, N is an integer greater than or equal to 2, andT is an integer greater than or equal to
 1. 11. A first communicationnode located in a vehicle, in a communication system supportingVehicle-to-Everything (V2X) communication, the first communication nodecomprising: processor; transceiver transmitting and receiving a signalaccording to control of the processor; and memory storing one or moreinstructions which are executed by the processor; wherein the one ormore instructions are configured to: perform V2X communication with asecond communication node using an original resource according to anoriginal Semi-Persistent Scheduling (SPS) configuration set by a servingbase station; when a congestion level in the original resource isgreater than or equal to a predetermined threshold and at least onetarget base station supporting the V2X communication is discovered,transmit user equipment (UE) assistance information including at leastone identifier of the at least one target base station to the servingbase station; receive, from the serving base station, a messageincluding a new SPS configuration to be applied to the serving basestation and the at least one target base station; perform a messagetransmission and reception procedure with the at least one target basestation for delivery of the new SPS configuration; and perform the V2Xcommunication with the second communication node using a first resourcescheduled by the serving base station based on the new SPS configurationand a second resource scheduled by the at least one target base stationbased on the new SPS configuration.
 12. The first communication nodeaccording to claim 11, wherein the UE assistance information furtherincludes an indicator requesting load distribution using the at leastone target base station.
 13. The first communication node according toclaim 11, wherein the message including a new SPS configuration is aradio resource control (RRC) connection reconfiguration message.
 14. Thefirst communication node according to claim 11, wherein, in the messagetransmission and reception procedure, the one or more instructions areconfigured to: transmit, to the at least one target base station, an RRCconnection request message requesting a connection for applying the newSPS configuration; receive an RRC connection setup message from the atleast one target base station, the RRC connection setup message being aresponse to the RRC connection request message; transmit an RRCconnection setup complete message including an identifier of the servingbase station and the new SPS configuration to the at least one targetbase station when a connection establishment between the firstcommunication node and the at least one target base station iscompleted; and receive, from the at least one target base station, anRRC connection reconfiguration message indicating an application of thenew SPS configuration.
 15. The first communication node according toclaim 11, wherein, in the message transmission and reception procedure,the one or more instructions are configured to: transmit, to the atleast one target base station, UE assistance information including anindicator requesting application of the new SPS configuration, anidentifier of the serving base station, and the new SPS configuration;and receive, from the at least one target base station, an RRCconnection reconfiguration message indicating an application of the newSPS configuration.
 16. The first communication node according to claim11, wherein a radio access technology (RAT) supported by the servingbase station is different from a RAT supported by the at least onetarget base station.
 17. The first communication node according to claim11, wherein, when a sum of a number of serving base stations and anumber of the at least one target base station is N and a transmissioninterval of the original SPS configuration is T transmission timeintervals (TTIs), a transmission interval of the new SPS configurationis set to Nx T TTIs, N is an integer greater than or equal to 2, and Tis an integer greater than or equal to
 1. 18. The first communicationnode according to claim 17, wherein an offset between transmissionintervals of the N base stations is set to T TTIs in the new SPSconfiguration.
 19. The first communication node according to claim 11,wherein, when a sum of a number of serving base stations and a number ofthe at least one target base station is N and a transmission interval ofthe original SPS configuration is T TTIs, a transmission interval of thenew SPS configuration is set to T TTIs, a size of data to be transmittedthrough each of the N base stations in the new SPS configuration equals(a size of total data to be transmitted to the second communicationnode)/N, N is an integer greater than or equal to 2, and T is an integergreater than or equal to
 1. 20. The first communication node accordingto claim 11, wherein, when a sum of a number of serving base stationsand a number of the at least one target base station is N and atransmission interval of the original SPS configuration is T TTIs, atransmission interval of the new SPS configuration is set to T TTIs, asize of data to be transmitted through each of the N base stations inthe new SPS configuration is inversely proportional to a channelcongestion of each of the N base stations, N is an integer greater thanor equal to 2, and T is an integer greater than or equal to
 1. 21. Anoperation method of a first communication node located in a vehicle, ina communication system supporting Vehicle-to-Everything (V2X)communication, the operation method comprising: performing V2Xcommunication with a second communication node using an originalresource according to an original Semi-Persistent Scheduling (SPS)configuration set by a first base station; receiving, from the firstbase station, a message including a new SPS configuration to be appliedto the first base station and at least one second base station which isconnected to the first communication node; and performing the V2Xcommunication with the second communication node using a first resourcescheduled by the first base station connected to the first communicationnode based on the new SPS configuration instead of the original SPSconfiguration and a second resource scheduled by the at least one secondbase station connected to the first communication node based on the newSPS configuration instead of the original SPS configuration.
 22. Theoperation method according to claim 21, wherein the message including anew SPS configuration is a radio resource control (RRC) connectionreconfiguration message.
 23. The operation method according to claim 21,wherein a radio access technology (RAT) supported by the first basestation is different from a RAT supported by the at least one secondbase station.
 24. The operation method according to claim 21, wherein,when a sum of a number of first base stations and a number of the atleast one second base station is N and a transmission interval of theoriginal SPS configuration is T transmission time intervals (TTIs), atransmission interval of the new SPS configuration is set to N×T TTIs, Nis an integer greater than or equal to 2, and T is an integer greaterthan or equal to
 1. 25. The operation method according to claim 24,wherein an offset between transmission intervals of the N base stationsis set to T TTIs in the new SPS configuration.
 26. The operation methodaccording to claim 21, wherein, when a sum of a number of first basestations and a number of the at least one second base station is N and atransmission interval of the original SPS configuration is T TTIs, atransmission interval of the new SPS configuration is set to T TTIs, asize of data to be transmitted through each of the N base stations inthe new SPS configuration equals (a size of total data to be transmittedto the second communication node)/N, N is an integer greater than orequal to 2, and T is an integer greater than or equal to
 1. 27. Theoperation method according to claim 21, wherein, when a sum of a numberof first base stations and a number of the at least one second basestation is N and a transmission interval of the original SPSconfiguration is T TTIs, a transmission interval of the new SPSconfiguration is set to T TTIs, a size of data to be transmitted througheach of the N base stations in the new SPS configuration is inverselyproportional to a channel congestion of each of the N base stations, Nis an integer greater than or equal to 2, and T is an integer greaterthan or equal to
 1. 28. A first communication node located in a vehicle,in a communication system supporting Vehicle-to-Everything (V2X)communication, the first communication node comprising: processor;transceiver transmitting and receiving a signal according to control ofthe processor; and memory storing one or more instructions which areexecuted by the processor; wherein the one or more instructions areconfigured to: perform V2X communication with a second communicationnode using an original resource according to an original Semi-PersistentScheduling (SPS) configuration set by a first base station; receive,from the first base station, a message including a new SPS configurationto be applied to the first base station and at least one second basestation which is connected to the first communication node; and performthe V2X communication with the second communication node using a firstresource scheduled by the first base station connected to the firstcommunication node based on the new SPS configuration instead of theoriginal SPS configuration and a second resource scheduled by the atleast one second base station connected to the first communication nodebased on the new SPS configuration instead of the original SPSconfiguration.
 29. The first communication node according to claim 28,wherein, when a sum of a number of first base stations and a number ofthe at least one second base station is N and a transmission interval ofthe original SPS configuration is T transmission time intervals (TTIs),a transmission interval of the new SPS configuration is set to N×T TTIs,N is an integer greater than or equal to 2, and T is an integer greaterthan or equal to
 1. 30. The first communication node according to claim28, wherein, when a sum of a number of first base stations and a numberof the at least one second base station is N and a transmission intervalof the original SPS configuration is T TTIs, a transmission interval ofthe new SPS configuration is set to T TTIs, a size of data to betransmitted through each of the N base stations in the new SPSconfiguration equals (a size of total data to be transmitted to thesecond communication node)/N, N is an integer greater than or equal to2, and T is an integer greater than or equal to
 1. 31. The firstcommunication node according to claim 28, wherein, when a sum of anumber of first base stations and a number of the at least one secondbase station is N and a transmission interval of the original SPSconfiguration is T TTIs, a transmission interval of the new SPSconfiguration is set to T TTIs, a size of data to be transmitted througheach of the N base stations in the new SPS configuration is inverselyproportional to a channel congestion of each of the N base stations, Nis an integer greater than or equal to 2, and T is an integer greaterthan or equal to 1.